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audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker() 

Currently @audit_context is allocated twice for io_uring workers:

  1. copy_process() calls audit_alloc();
  2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
     is effectively audit_alloc()) and overwrites @audit_context,
     causing:

  BUG: memory leak
  unreferenced object 0xffff888144547400 (size 1024):
<...>
    hex dump (first 32 bytes):
      00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    backtrace:
      [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
      [<ffffffff81239e63>] copy_process+0xcd3/0x2340
      [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
      [<ffffffff81686604>] create_io_worker+0xb4/0x230
      [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
      [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
      [<ffffffff816768b3>] io_queue_async+0x113/0x180
      [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
      [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
      [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
      [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
      [<ffffffff8125a688>] get_signal+0xc18/0xf10
      [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
      [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
      [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
      [<ffffffff844a7e80>] do_syscall_64+0x40/0x80

Then,

  3. io_sq_thread() or io_wqe_worker() frees @audit_context using
     audit_free();
  4. do_exit() eventually calls audit_free() again, which is okay
     because audit_free() does a NULL check.

As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
redundant audit_free() calls.

Fixes: 5bd2182d58 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
Suggested-by: Paul Moore <paul@paul-moore.com>
Cc: stable@vger.kernel.org
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20220803222343.31673-1-yepeilin.cs@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Peilin Ye 2022-08-03 15:23:43 -07:00 committed by Jens Axboe
parent ff2557b722
commit f482aa9865
4 changed files with 0 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/audit.h
View File

@ -285,7 +285,6 @@ static inline int audit_signal_info(int sig, struct task_struct *t)
/* These are defined in auditsc.c */
/* Public API */
extern int audit_alloc(struct task_struct *task);
extern int audit_alloc_kernel(struct task_struct *task);
extern void __audit_free(struct task_struct *task);
extern void __audit_uring_entry(u8 op);
extern void __audit_uring_exit(int success, long code);
@ -578,10 +577,6 @@ static inline int audit_alloc(struct task_struct *task)
{
return 0;
}
static inline int audit_alloc_kernel(struct task_struct *task)
{
return 0;
}
static inline void audit_free(struct task_struct *task)
{ }
static inline void audit_uring_entry(u8 op)

3
io_uring/io-wq.c
View File

@ -624,8 +624,6 @@ static int io_wqe_worker(void *data)
snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid);
set_task_comm(current, buf);
audit_alloc_kernel(current);
while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
long ret;
@ -660,7 +658,6 @@ static int io_wqe_worker(void *data)
if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
io_worker_handle_work(worker);
audit_free(current);
io_worker_exit(worker);
return 0;
}

4
io_uring/sqpoll.c
View File

@ -235,8 +235,6 @@ static int io_sq_thread(void *data)
set_cpus_allowed_ptr(current, cpu_online_mask);
current->flags |= PF_NO_SETAFFINITY;
audit_alloc_kernel(current);
mutex_lock(&sqd->lock);
while (1) {
bool cap_entries, sqt_spin = false;
@ -310,8 +308,6 @@ static int io_sq_thread(void *data)
io_run_task_work();
mutex_unlock(&sqd->lock);
audit_free(current);
complete(&sqd->exited);
do_exit(0);
}

25
kernel/auditsc.c
View File

@ -1073,31 +1073,6 @@ int audit_alloc(struct task_struct *tsk)
return 0;
}
/**
* audit_alloc_kernel - allocate an audit_context for a kernel task
* @tsk: the kernel task
*
* Similar to the audit_alloc() function, but intended for kernel private
* threads. Returns zero on success, negative values on failure.
*/
int audit_alloc_kernel(struct task_struct *tsk)
{
/*
* At the moment we are just going to call into audit_alloc() to
* simplify the code, but there two things to keep in mind with this
* approach:
*
* 1. Filtering internal kernel tasks is a bit laughable in almost all
* cases, but there is at least one case where there is a benefit:
* the '-a task,never' case allows the admin to effectively disable
* task auditing at runtime.
*
* 2. The {set,clear}_task_syscall_work() ops likely have zero effect
* on these internal kernel tasks, but they probably don't hurt either.
*/
return audit_alloc(tsk);
}
static inline void audit_free_context(struct audit_context *context)
{
/* resetting is extra work, but it is likely just noise */